Charging mechanism for gas powered firearms

ABSTRACT

An improved mechanism for charging a gas powered firearm, especially with regard to the Kalashnikov variants of rifles known as AK-47s, comprising a modified gas tube having a lateral aperture formed into its left side, a sleeve suitably adapted to fit within the modified gas tube over the shaft of the operating rod, and a modified charging handle suitably adapted to connect to the sleeve and to extend from the firearm through the lateral aperture, such that the firearm may be manually charged from the left side by drawing the charging handle rearward; and providing safety improvements and a method of retrofitting firearms.

This application is a Continuation in Part of U.S. patent application Ser. No. 12/540,443, filed Aug. 13, 1999, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates generally to firearms, and specifically to an improved mechanism for charging a firearm, especially with regard to the variants of Kalashnikov rifles generally referred to as AK-47 models.

BACKGROUND

AK-47 rifles are gas operated firearms in which the discharge gases from a fired round of ammunition serve to cycle the firearm's bolt and automatically eject the spent cartridge casing from the just fired round and to chamber the next round from a magazine. The standard charging mechanism of an AK-47 is fairly straightforward. These firearms comprise a barrel in communication with a firing chamber, or breach, and a bolt used to provide access to the breach. The barrel is fitted with a port or similar aperture which permits a portion of the discharge gases created from the firing of a round of ammunition to escape the barrel through the port. The port is in communication with an adjacent gas block, which in turn is in communication with an adjacent, substantially cylindrical gas tube. Contained within the gas tube is an gas piston. The gas piston has a forward piston portion having an outside diameter substantially the same, but slightly smaller, as the inside diameter of the gas tube. The rearward end of the gas piston is in sliding connection with the bolt assembly. The gas piston is designed to reciprocate between a forward and rearward position within the gas tube, with its rearward movement designed to simultaneously force the bolt assembly rearward, which in turn compresses a recoil spring mechanism. The recoil spring mechanism, in turn, forces the bolt assembly to return forward to its firing position which, in turn, moves the gas piston forward within the gas tube.

A standard AK-47 must be charged in order to operate. Charging of the firearm comprises the loading and reloading of ammunition into the firing chamber and occurs as a result of a cycling of the bolt assembly described above. During operation, charging is occurs automatically utilizing the discharge gases of a fired round of ammunition. When a round is fired, the cartridge casing remains in the chamber of the barrel as the gases formed by the explosion force the bullet to travel down the length of the barrel. As the bullet passes the barrel port, a predetermined portion of the discharge gases escape through the port and pass through the gas block into the gas tube, where they then impinge upon the piston portion of the gas piston, driving it rearward. This rearward travel of the gas piston moves the bolt rearward, opening the breach, extracting the spent cartridge casing from the breach, ejecting the spent cartridge from the ejection port of the weapon and compressing the recoil spring mechanism in connection with the rear portion of the bolt. While the bolt is thus in its rearward position and the breach is opened, a new round may be readied into the breach by action of a spring mechanism in an ammunition magazine. As the bolt returns forward the uppermost round from the ammunition magazine is stripped therefrom and fed into the chamber of the barrel. This cycling process typically continues until all of the ammunition is expended and both the ammunition magazine and the firing chamber are emptied.

The automatic loading cycle of each round of ammunition described above takes place upon the firing of the previous round. However, since the normal position of the firearm at rest is with the bolt in a closed position, urged forward by the recoil spring mechanism, the initial charging of the firearm must be accomplished manually. Initial charging of a standard AK-47 is accomplished by manually drawing the bolt assembly rearward. This is done by manually grasping and drawing back a charging handle located on the right rear side of the AK-47, which is directly linked to the bolt assembly. Manually cycling the charging handle rearwardly first “cocks” the firing mechanism and then releasing it results in the loading of a round from the magazine into the breach as described above. Once the bolt returns forward to its completely closed position, the firearm is loaded and ready for firing. In addition to manually charging an AK-47 for an initial round, it may also be necessary to manually charge the weapon due to a misfire or misfeed of a round from the magazine to clear a defective round from the breach.

The current state of the art for manually charging an AK-47 is less than ideal. One significant issue is due to the charging handle being located on the right side of the firearm. A right-handed operator typically holds the pistol grip of the firearm with their right hand and supports the front stock portion of the firearm with their left. Under operational conditions, such as during combat or during sporting events where time is of the essence, the butt of the rifle preferably remains in firing position against operator's right shoulder with the right hand remaining on the pistol grip at all times. In this operational condition, the left hand is used to reload the weapon with a fresh magazine and then manually charge the firearm. In order to manually charge the firearm in this manner, the operator's left hand must move from the barrel supporting position, over or under the firearm receiver to grasp the charging handle. The use of the left hand in the described manner enables the operator to keep their right hand on the pistol grip in a ready to fire position, but usually results in the loss of sight picture and an unbalanced firearm because of the awkward movement of the operator's left hand over or under the receiver to the right side to engage the charging handle. This method of charging the AK-47 not only runs the risk of losing the site picture but also results in slower charging due to the amount of distance the left hand must travel.

Another deficiency of the charging mechanism of the standard AK-47 rifle is that the gas tube of the standard AK-47 rifle has a closed cylindrical configuration. It has no opening to allow for easy access to its interior for purposes of cleaning or allowing air flow to cool the firearm. Since the discharge gases contain spent powder residue, the greatest amount of debris and fouling occurs within the gas block and the interior of the gas tube. This residue stays in the gas tube and tends to accumulate after each round is fired. If the gas tube and gas block are not periodically cleaned, the charging mechanism of the firearm will fail to operate properly, resulting in improper or even unsafe operation of the weapon. In order to clean this residue the firearm must be disassembled so that a cleaning cloth can be inserted into the gas tube. This is a time consuming operation and requires frequent periods of inactivity of use of the firearm. Moreover, the closed configuration of the gas tube prevents ready visual inspection of the firing chamber, that is, one cannot visually inspect the chamber to determine whether cleaning is needed or even if a round is loaded therein without some degree of disassembly of the firearm. This presents a potential safety issue.

Another deficiency of the charging mechanism of the standard AK-47 rifle is that the receiver is not provided with a bolt locking mechanism, that is, at rest the bolt is always positioned forward in its closed position, pressing against the chamber as a result of the urging by the recoil spring mechanism. On the standard AK-47 there is no way to keep the bolt open unless the operator manually applies a constant rearward force on the charging handle. Upon the operator releasing the charging handle (intentional or not) the bolt assembly, under pressure from the recoil spring mechanism, rapidly returns to its forward, closed, position.

The standard AK-47 rifle is provided with a safety lever located on the right side of the receiver of the firearm proximate the charging handle. When the safety lever is engaged in its “safe” position, the trigger and associated firing mechanism are locked and cannot be actuated. So positioned the safety lever also serves to block the rearward travel of the charging handle. This prevents the charging handle from being fully drawn rearwardly to chamber a round when the safety lever is engaged. In order to charge the firearm the safety lever must be disengaged, resulting in the trigger not being locked during charging. This presents another potential safety issue.

The basic design of the AK-47 rifle described above also pertains to other popular gas operated firearms, such as the various Kalashnikov variants (AK-74, AK-101, AK-103, and others), the Samozaryadniy Karabin sistemi Simonova (SKS) rifle and its variants, and the Fusil Automatique Leger-Light Automatic Rifle (FN-FAL) and its variants, as well as other designs. In this respect, to the extent the deficiencies described above also apply to these other gas operated firearms, the remediation which is addressed by the present invention applies to these firearms as well.

There thus remains a need for an improved charging mechanism for a gas operated firearm that is more efficiently actuable for right-handed operators, improves the safety profile of the firearm, provides for easier inspection and cleaning, is simple and cost effective to manufacture and which readily retrofits into existing firearms.

SUMMARY

An aspect of the present invention discloses repositioning of the charging handle of a gas operated firearm to the left side of the firearm, further forward than the standard positioning of the charging handle. This accomplishes two purposes. First, by positioning the charging handle on the left side of the firearm, a right-handed operator need not reach around over the top or underneath the firearm with the left hand to reach the charging handle. Rather, the charging handle is proximate to the left hand, allowing for easier and quicker grasping of same. Second, by positioning the charging handle further forward on the firearm, the charging handle is closer to the operator's left hand when it is supporting the barrel, allowing for a smoother transition of the left hand from barrel to charging handle, reducing barrel movement and loss of sight picture.

Another aspect of the present invention is to form into the left side of a standard gas tube a lateral aperture running along the longitudinal axis of the gas tube. The forward edge of the aperture is located rearward of the forward portion of the gas piston, such that the forward portion of the gas piston remains in a closed portion of the gas tube when the gas piston is in the forward position. The aperture allows access into the gas tube and access to the shaft of the gas piston. As such, when the bolt assembly is drawn rearward, the breach may be visually inspected through the lateral aperture to determine whether there is a round in the firing chamber. In addition, when the bolt assembly is drawn rearward the forward portion of the gas tube, the bore, and the chamber become accessible, allowing for cleaning of those portions of the firearm without need for further disassembly. Access to the inside of the gas tube through the aperture also acts as a means for faster cooling of the firearm, as now outside air can circulate inside the gas tube. This improves operation of the firearm, which tends to build up heat from the friction of the bullets moving along the barrel and the heat from the discharge gases after a substantial amount of ammunition is fired. It also allows for more efficient venting of the discharge gases after they have accomplished the task of moving the gas piston rearward. As the forward portion of the gas piston moves rearward past the front edge of the lateral aperture, the gases escape through the lateral aperture. This eliminates the need for a specially configured discharge configuration to vent the gases from the firearm.

Another aspect of the present invention is to introduce a semi-cylindrical sleeve onto the shaft of the gas piston. The sleeve provides an attachment for the charging handle, which extends through the lateral aperture of the gas tube. The rear portion of the sleeve impinges against the rear portion of the gas piston, such that when the sleeve is moved rearward, the gas piston, and the bolt assembly in connection therewith, are moved rearward with it. The combination of the lateral aperture formed into the left side of the gas tube, the sleeve fitted over the shaft of the gas piston, and the charging handle attached to the sleeve and extending from the left side of the firearm represent the basic configuration of the improved charging mechanism. This basic configuration may be easily retrofitted to existing firearms by simply substituting the modified gas tube for a standard gas tube and adding the sleeve and charging handle. The present invention contemplates such a conversion kit for retrofitting firearms, comprising the modified gas tube, the sleeve, and the charging handle.

Another aspect of the present invention is to introduce a locking bifurcated sleeve onto the shaft of a gas piston. The sleeve is confrontable by a charging tube connected to a charging handle which extends through a lateral aperture of the gas tube. The rear portion of the sleeve impinges against the rear portion of the gas piston, such that when the charging tube is moved rearwardly, the gas piston and the bolt assembly in connection therewith, are moved rearwardly as well. The combination of the lateral aperture formed into the left side of the gas tube, the locking sleeve fitted over the shaft of the gas piston, and the charging tube confronting the sleeve during a charging cycle and having a charging handle attached thereto, extending from the left side of the firearm represent one embodiment of the improved charging mechanism. This basic configuration may be easily retrofitted to existing firearms by simply substituting the modified gas tube for a standard gas tube and installing the locking sleeve around the shaft of the gas piston and installing a charging tube and handle within the modified gas tube. The present invention contemplates such a conversion kit for retrofitting firearms, comprising the modified gas tube, the locking sleeve, the charging tube and charging handle.

Another aspect of the present invention is to introduce a modified gas piston having a rearward cylindrical block machined directly into the shaft in lieu of a locking bifurcated sleeve. The cylindrical block is confrontable by a charging tube connected to a charging handle which extends through a lateral aperture of the gas tube much the same as the bifurcated sleeve. When the charging tube is moved rearwardly by drawing on the charging handle, the charging tube confronts the cylindrical block of the gas piston and thus it and the bolt assembly in connection therewith, are moved rearwardly as well. The combination of the lateral aperture formed into the left side of the gas tube, the modified shaft of the gas piston having a cylindrical block, and the charging tube configured to confront the cylindrical block during a charging cycle and having a charging handle attached thereto, extending from the left side of the firearm represent another embodiment of the improved charging mechanism. This basic configuration may be easily retrofitted to existing firearms by simply substituting the modified gas tube for a standard gas tube and installing the modified gas piston with cylindrical block and installing a charging tube and handle within the modified gas tube. The present invention contemplates such a conversion kit for retrofitting firearms, comprising the modified gas tube, the modified gas tube, the charging tube and charging handle.

In addition to the basic aspects of the present invention described above, another aspect of the present invention is to form a notch into the lateral aperture proximate to the rear edge of the aperture, with the notch configured to receive and hold the shaft of the charging handle. When the charging handle is moved rearward, as it becomes aligned with the notch the charging handle may be rotated upward such that its shaft fits into the notch. The notch then holds the charging handle in place, under tension by the recoil spring mechanism. This results in effectively holding the gas piston and the bolt assembly in place in the open breach position. The charging handle is able to rotate upwards due to the semi-cylindrical configuration of the sleeve, which is free to rotate about the shaft of the gas piston. So designed, the notch acts as a bolt lock. The bolt lock serves as an additional safety mechanism, as the firearm cannot fire a round when the bolt is locked in the open breach position. It also improves safety by allowing a visual inspection of the breach to see whether there is a round chambered therein (which could occur even if the ammunition magazine is empty or removed from the firearm). By locking the bolt in the open breach position, the forward portion of the gas tube, the bore, and the chamber can be easily cleaned through the lateral aperture, as described above. The bolt lock is released by rotating the charging handle shaft downward and out of the notch, so that it rides within the lateral aperture. Releasing the charging handle from the notch causes the recoil spring mechanism to force the bolt assembly, the gas piston, and the charging handle forward, resulting in the breach closing. The bolt lock can be easily released with just the thumb of the left hand, thereby allowing the firearm to be charged without removing the left hand from the barrel, minimizing barrel movement and loss of sight picture.

Another aspect of the present invention is to allow the charging handle to fold forward, out of the way when not in use. Another aspect of the present invention contemplates the removal of the standard right side charging handle, thereby freeing the bolt assembly to move rearward even when the safety lever is engaged. Thus, the firearm can have its safety lever engaged with the trigger locked while the operator chambers a round. No longer is it required for the safety to be disengaged in order to chamber a round. When the operator is ready to fire, the safety can be disengaged. These aspects further improve the safety profile of the firearm.

The improved charging mechanism allows a right-handed operator to charge the firearm more easily. He or she no longer has to reach over or under to charge the rifle. The charging handle is now in a convenient location, proximate to the position where the operator must place the left hand while firing. This allows not only faster reloading then the existing configuration, but safer reloading. The operator no long has to worry about losing sight picture or unbalancing the firearm when charging the firearm. The charging handle is also in an improved location for carrying the firearm when it is slung across the chest by a sling strap. By being located further forward on the firearm, the charging handle is no longer in a spot where it may harm the operator if the firearm is forced into the chest, for example if the operator falls onto the firearm while carrying it by its sling.

The present invention also contemplates a method of retrofitting gas operated firearms to use the improved charging mechanism disclosed herein. The method includes the steps of obtaining a modified gas tube as disclosed above; obtaining a sleeve as disclosed above; obtaining a modified charging handle as disclosed above; disassembling the firearm, at least to the extent of removing the original gas tube and the gas piston; placing the sleeve over the shaft of the gas piston; reassembling the firearm, whereby the modified gas tube is substituted for the original gas tube and the gas piston with the sleeve placed over its shaft is inserted into the modified gas tube; and attaching the modified charging handle to the sleeve, with the optional step of removing the original charging handle from the right side of the firearm.

It is therefore an object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm which adds safety features to the firearm.

It is a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm which is easier to use for right-handed operators.

It is yet a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm that is easy to clean and maintain.

It is yet a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm which is easy to manufacture.

It is yet a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm which is easy to retrofit to an existing firearm.

It is yet a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm which allows for faster loading and more accurate operation of the firearm.

It is yet a further object of an aspect of the invention to provide an improved charging mechanism for a gas operated firearm that improves the durability of the firearm by reducing harmful heat buildup.

It is yet a further object of an aspect of the invention to provide a method for retrofitting a gas operated firearm with an improved charging mechanism.

Other objects of this invention will be apparent to those skilled in the art from the description and claims which follow.

DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of the right side of a prior art charging mechanism for a gas operated firearm. The gas piston is shown within the gas tube in phantom lines. A cutaway of the barrel exposes the gas port;

FIG. 2 is a partial side view of the left side of a prior art charging mechanism for a gas operated firearm. A cutaway of the barrel exposes the gas port;

FIG. 3 is a top view of a prior art charging mechanism for a gas operated firearm. The gas piston is shown within the gas tube in phantom lines. A cutaway of the barrel exposes the gas port;

FIG. 4 is a partial side view of the left side of one aspect of an embodiment of the present invention. A cutaway of the barrel exposes the gas port;

FIG. 5 is a side view of the gas piston, bolt assembly, and recoil spring mechanism of one aspect of an embodiment of the present invention, with the sleeve placed over the shaft of the gas piston, which is shown in phantom;

FIG. 6 is a rear cutaway view of the gas tube, sleeve, and gas piston shown in FIG. 5 taken through section A-A;

FIG. 7 is a partial side view of the left side of one aspect of an embodiment of the present invention with the charging handle drawn back and rotated into the notch, depicting the gas piston in a rearward position with the interior of the gas tube exposed;

FIG. 8 is a perspective partial side view of the left side of one aspect of an embodiment of the present invention with the charging handle drawn back and rotated into a cocking notch wherein the weapon is maintained in an open bolt condition and depicting the interior of the gas tube exposed. A cutaway of the barrel exposes the gas port;

FIG. 9 is a partial top view of one aspect of an embodiment of the present invention depicting an alternative embodiment of the charging handle, with phantom lines showing the direction of hinged motion and the folded position of the gripping member of the charging handle;

FIG. 10A is a partial side view of the left side of one aspect of an embodiment of the present invention depicting another alternative embodiment of the charging handle, with phantom lines showing the direction of pivoting motion and the forward position of the gripping member of the charging handle;

FIG. 10B is a rear cutaway view of the gas tube, sleeve, and gas piston of the embodiment shown in FIG. 10A taken through section B-B;

FIG. 11 is a side view of one aspect of an embodiment of the present invention depicting the modified gas tube, the sleeve, and one embodiment of the modified charging handle;

FIG. 12 is a rear cutaway view of one aspect of an embodiment of the present invention depicting the sleeve and another embodiment of the modified charging handle;

FIG. 13 is a perspective view of one aspect of an embodiment of the present invention depicting a modified gas tube, a charging handle and tube, bifurcated sleeve members and a locking bushing;

FIG. 14 is a perspective view of one aspect of an embodiment of the present invention depicting a modified gas tube, charging components within the gas tube and a sight rail located atop of the gas tube;

FIG. 15 is a perspective view of an aspect of one embodiment of the present invention depicting the shaft of the gas piston of a firearm being engaged by bifurcated sleeve members and locking bushing, in mating alignment with the charging tube;

FIG. 16 is a perspective view of an aspect of one embodiment of the present invention depicting modified gas piston of a firearm including a cylindrical block, in mating alignment with the charging tube;

FIG. 17 is a perspective view of an AK-47 style weapon with its dust cover and recoil spring assembly removed, a locked bifurcated sleeve mounted around the shaft of the gas piston, oriented to be inserted into the receiver and modified gas tube in accordance with an aspect of one embodiment of the present invention; and

FIG. 18 is a partial elevational view of an AK-47 style weapon having a modified gas tube and charging system according to an embodiment of the present invention with the charging handle retained by the cocking notch in a locked, open bolt condition.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a representative AK-47 style weapon according to the art is there disclosed. The present invention is intended to modify a gas operated firearm 1 having at least the following components: a barrel 10, a receiver 22, a trigger 90, a firing chamber 30, a bolt assembly 40, a recoil spring assembly 50, a gas piston 300, an ammunition magazine 60, a port 70 formed into the barrel 10, a gas block 100, a gas tube 34, and a charging handle 32. See The firearm 1 may also comprise a pistol grip 20, butt stock 24 (see FIG. 16) and a safety 80.

In operation, the bolt assembly 40 of the firearm 1 is suitably adapted to reciprocated between forward and rearward positions, with its rearward movement causing a round of ammunition to be moved into the firing chamber 30 and its forward movement aligning the firing mechanism of the firearm 1 to permit firing of the round of ammunition. The movement of a round of ammunition into the firing chamber 30 and readying it for firing is known as charging the firearm 1. The gas piston 300 of the firearm 1 is located within the gas tube 34 and is suitably adapted to reciprocate forward and rearward within the gas tube. Being further in connection with the front portion 42 of the bolt assembly 40 the gas piston 300 in cooperation with bolt carrier 46 is suitably adapted to move the bolt assembly 40 in a rearward direction. See FIGS. 3 and 5. The gas piston 300 is rigid and substantially cylindrical, having a forward portion 302, a rear portion 304, and a shaft 310 interposed between the forward portion and the rear portion, with the outside diameter of the shaft 310 less than the outside diameter of either the forward portion 302 or the rear portion 304 of the gas piston 300. The recoil spring mechanism 50 of the firearm 1 is in connection with the bolt carrier 46 and is suitably adapted to bias the bolt assembly 40 in a forward direction upon being compressed when the bolt assembly is moved in a rearward direction. The ammunition magazine 60 has a spring loading mechanism suitably adapted to move a round of ammunition upward and ready to be stripped from the magazine by the forward motion of the bolt and directed into the firing chamber 30 of the firearm 1 when the bolt assembly has been released from its rearward position.

The port 70 formed into the barrel 10 of the firearm 1 provides a communication between the barrel 10 and the gas tube 34 via the gas block 100, through which a portion of the gas generated by the firing of a round of ammunition may pass. This discharge gas passing out of the barrel 10 through the port 70 and gas block 100 into the gas tube 34 exerts a pressure against the forward portion 302 of the gas piston 300 urging it rearward, thereby simultaneously moving the bolt carrier 46 rearward. The movement of the bolt carrier 46 rearward by the gas piston 300, followed by the forward movement of the bolt assembly 40 by the recoil spring mechanism 50, constitutes an automatic charging cycle of the firearm 1 by gas operation. Alternatively, the charging handle 32 may be used by the operator to manually draw the bolt carrier 46 rearward, constituting a manual charging cycle. A manual charging cycle is necessary to prepare the firearm 1 for firing a round of ammunition upon reloading or in the event of a misfire or misfeed.

Variations on the specifics of the foregoing basic firearm components may be found, but the described functionality should be present. Examples of firearms having these basic components are the Kalashnikov (AK-47) rifle and its variants, the Kalashnikov (AK-74) rifle and its variants, the Kalashnikov (AK-101) rifle and its variants, the Kalashnikov (AK-103) rifle and its variants, the Samozaryadniy Karabin sistemi Simonova-style (SKS) rifle, and the Fusil Automatique Leger-Light Automatic Rifle (FN-FAL) rifle. The present invention may be used to retrofit other similarly configured gas operated firearms.

Referring to FIG. 4, the improved charging mechanism of one embodiment of the present invention comprises a modified gas tube 200, a sleeve 500, and a modified charging handle 400. The modified gas tube 200 is in communication with the gas block 100 such that a portion of the gas created from the firing of a round of ammunition is discharged from the barrel 10 through port 70, through the gas block 100 and into the modified gas tube 200 to impinge upon the front face portion 302 of gas piston 300. The modified gas tube 200 has a substantially cylindrically shaped interior 210 with a substantially constant inside diameter which is sized to be slightly greater that the diameter of the face portion 302 of the gas piston 300. The modified gas tube 200 of the present invention is suitably adapted to accommodate within its interior 210 the gas piston 300, which reciprocates forward and rearward within the modified gas tube 200. The inside diameter of the modified gas tube 200 should be substantially the same as, but just slightly less than, the outside diameter of the forward portion 302 of the gas piston 300. A snug fit between the forward portion 302 of the gas piston 300 and the modified gas tube 200 minimizes the potential for discharge gases entering the gas tube from the gas block 100 to leak around the forward portion of the gas piston, thereby maximizing the force of the discharge gases against the forward portion of the gas piston. The inside surface of modified gas tube 200 and the outside surface of the forward portion 302 of the gas piston 300 may be polished or otherwise treated, such as with a lubricant, to minimize friction between the two mated surfaces.

The modified gas tube 200 further has a lateral aperture 220 formed along the majority of its left side, passing completely through the modified gas tube into its interior 210. See FIG. 4. The lateral aperture 220 runs parallel to the longitudinal axis of the modified gas tube 200 and has substantially parallel top and bottom edges 226, 228. The lateral aperture 220 provides access into the modified gas tube 200 of the present invention. This access allows cleaning of the forward portions of the modified gas tube 200 without disassembly of the firearm 1. In the preferred embodiment of the present invention, the front edge 222 of the lateral aperture 220 is located rearward of the location of the forward portion 302 of the gas piston 300 when the gas piston is in a forward position within the modified gas tube 200. That is, the lateral aperture 220 is located behind the forward portion 302 of the gas piston 300 when it is in the forward position. This prevents discharged gas from escaping from the modified gas tube 200 through the lateral aperture 220 when the gas piston 300 is in the forward position. As gas exerts a pressure on the forward portion 302 on the gas piston 300, urging it rearward, the forward portion of the gas piston moves alongside the lateral aperture 220 exposing the interior 210 of the modified gas tube 200, thereby allowing the gases to vent from the modified gas tube through the lateral aperture.

In one embodiment of the present invention the lateral aperture 220 of the modified gas tube 200 may be centered on the left side of the modified gas tube substantially midway between the top and the bottom of the modified gas tube (i.e., within a horizontal plane passing through the center of the modified gas tube). In another embodiment the lateral aperture 220 may be centered somewhat higher than the horizontal to the modified gas tube 200. In the preferred embodiment the lateral aperture 220 is centered not more than forty-five degrees) (45°) above the horizontal. See FIG. 6.

The lateral aperture 220 of the modified gas tube 200 may further comprise a notch 230, the notch being formed into the lateral aperture 220 along its top edge 226, proximate to its rear edge 224, thereby causing the lateral aperture to have an inverted “T” configuration. See FIG. 4. The notch 230 has a width suitably adapted to receive and retain the modified charging handle 400 of the present invention and place the host firearm in a bolt open condition. See FIGS. 4, 7, and 8.

The sleeve 500 of one embodiment of the present invention is arcuate in a substantially semi-cylindrical configuration, allowing the sleeve 500 to be placed onto the shaft 310 of the gas piston 300 within the modified gas tube 200. See FIGS. 6 and 11. As such, the sleeve 500 has an outside diameter substantially the same as but not greater than the inside diameter of the modified gas tube 200. The inside surface of the modified gas tube 200 and the outside surface of the sleeve 500 may be polished or otherwise treated, such as with a lubricant, to minimize friction between the two mated surfaces. The inside diameter of the sleeve 500 is substantially the same as but not less than the outside diameter of the shaft 310 of the gas piston 300. The length of the sleeve 500 is substantially the same as, but not longer than, the length of the shaft 310 of the gas piston 300, thereby allowing it to nest with the shaft of the gas piston. See FIGS. 5 and 6. In alternate embodiments of the present invention the arc of the outer surface of the sleeve 500 may be significantly less than one hundred eighty degrees) (180°), though preferably more than ninety degrees) (90°). The dimensions of the sleeve 500 are configured so that the gas piston 300, when the sleeve 500 is placed onto its shaft 310, will continue to fit into the modified gas tube 200 and reciprocate forward and rearward within the modified gas tube along with the gas piston. The sleeve 500 may rotate about the shaft 310 of the gas piston 300 when it is placed thereon. Because the rear portion 304 of the gas piston 300 has an outside diameter greater than the outside diameter of the shaft 310 of the gas piston 300, the rear portion 504 of the sleeve 500 will impinge against the front of the rear portion of the gas piston when the sleeve is placed onto the shaft of the gas piston and moved rearward. See FIG. 5. Movement of the sleeve 500 rearward therefore exerts pressure on the rear portion 304 of the gas piston 300 and moves the gas piston rearward.

The charging handle 400 of the present invention is suitably adapted to be attached to the sleeve 500, such that the charging handle extends from the sleeve through the lateral aperture 220 of the modified gas tube 200 from the left side of the firearm 1 when the sleeve is placed onto the shaft 310 of the gas piston 300 and the gas piston is placed within the modified gas tube. In one embodiment of the present invention, the charging handle 400 is attached to the sleeve 500 proximate to its forward end 502. See FIG. 5. In one embodiment of the present disclosure, the charging handle 400 is removably attached to the sleeve 500. The operator of the firearm 1 may draw the charging handle 400 rearward, which simultaneously moves the sleeve 500 rearward, effecting rearward pressure upon the rear portion 304 of the gas piston 300 and thereby moving the gas piston and the bolt carrier 46 rearward, thus initiating a manual charging cycle. After the bolt carrier 46 is drawn to the rear of the firearm 1, release of the charging handle 400 results in the recoil spring mechanism 50 urging the bolt carrier forward, stripping the next round of ammunition from the magazine 60 and feeding it into the firing chamber 30, while simultaneously moving the gas piston 300, the sleeve 500, and the charging handle forward, thus completing the manual charging cycle.

In embodiments of the present invention utilizing a cocking notch 230 formed into the lateral aperture 220, the notch is configured to be located rearward of the position of the charging handle 400 when the bolt carrier 46 is in its forward position. See FIG. 4. In such configurations, the charging handle 400 may be directed into the notch 230 by the operator as they draw the charging handle back until it is aligned with the notch and then moving the charging handle upward into the notch. See FIGS. 7, 8 and 18. The charging handle 400 is capable of being moved into cocking notch 230 because the sleeve 500 to which it is attached is capable of rotating about the shaft 310 of the gas piston 300. The recoil spring mechanism 50 exerts a force against the bolt carrier 46, which translates to the gas piston 300, the sleeve 500, and the charging handle 400, biasing the charging handle within cocking notch 230. In this configuration the notch 230 acts as a bolt open lock. The bolt carrier 46 and bolt assembly 40 are held in an open position and cannot be moved until the charging handle 400 removed from the cocking notch 230. The bolt lock therefore acts as an alternative safety mechanism. It also acts as a means for maintaining access to the firing chamber 30 through the lateral aperture 220 for cleaning purposes.

In one embodiment of the present invention the charging handle 400 comprises a shaft 410, whereby the shaft of the charging handle is suitably adapted to connect the charging handle to the sleeve 500. In one embodiment the shaft 410 of the charging handle 400 comprises threads 412 formed thereon and the sleeve 500 comprises a threaded aperture 516 formed therein, with the threaded aperture 516 of the sleeve suitably adapted to accommodate the threads formed onto the shaft of the charging handle. See FIG. 11. In this embodiment, the charging handle 400 is connected to the sleeve 500 by screwing the threaded shaft 410 of the charging handle into the threaded aperture 516 of the sleeve. In an alternate embodiment the sleeve 500 comprises a pin 510 extending laterally therefrom, with the pin having threads 512 formed thereupon. The shaft 410 of the charging handle 400 comprises an end 414 and a threaded aperture 416 formed into the end of the shaft of the charging handle, with the threaded aperture suitably adapted to accommodate the threads 512 formed onto the shaft of said pin 510. See FIG. 12. The charging handle 400 is thus connected to the sleeve 500 by screwing the threaded aperture 416 in the end 414 of the charging handle \ onto the threaded pin 510 of the sleeve. Other known configurations for removably attaching the shaft 410 of the charging handle 400 to the sleeve 500 are also contemplated by the present invention.

In the embodiments of the present invention in which the charging handle 400 comprises a shaft 410 and the modified gas tube 200 comprises a cocking notch 230, the width of the notch is suitably adapted to receive and retain the shaft of the charging handle. In other embodiments of the present invention the charging handle 400 comprises a gripping member 420 and a pivot mechanism 430, with the gripping member oriented substantially perpendicular to the shaft 410 of the charging handle. See FIGS. 10A and 10B. The pivot mechanism 430 connects the gripping member 420 to the shaft 410 of the charging handle 400, such that the pivot mechanism permits the gripping member of the charging handle to be rotated forward toward the front of the firearm 1 in a substantially horizontal orientation and rotated rearward to extend substantially vertically. In yet other embodiments of the present invention the charging handle 400 comprises a gripping member 420 and a hinge mechanism 440, with the hinge mechanism suitably adapted to permit the gripping member of the charging handle to be folded forward toward the firearm 1 and unfolded to extend substantially perpendicularly from the firearm 1. In the embodiments of the present invention that utilize a reciprocating charging handle 400, it is desirable to pivot the gripping member 420 of the charging handle parallel to the modified gas tube 200, thus reducing the risk of the operator coming into inadvertent contact with the reciprocating charging handle. See FIG. 9. In yet other embodiments of the present invention the charging handle 400 is angled to provide a more comfortable grip for the operator's hand. Other configurations of the reciprocating charging handle 400 are also contemplated.

One aspect of the present invention also contemplates a method of retrofitting a gas operated firearm 1. The firearm 1 comprises a barrel 10, a receiver 22, a firing chamber 30, a bolt assembly 40 within a bolt carrier 46, a recoil spring mechanism 50 in connection with a rear portion 44 of the bolt carrier, a right side charging handle 32 extending from the front of the bolt carrier, a gas piston 34 in connection with a front portion 42 of the bolt assembly 40, an ammunition magazine 60 having a spring loading mechanism, a port 70 formed into the barrel 10 providing a communication between the barrel 10 and a gas block 100, and a closed gas tube in connection with the gas block 100, all as described above.

The method of retrofitting the gas operated firearm 1 comprises the steps:

A. obtaining a modified gas tube 200 having the characteristics and functions described above, see FIG. 11;

B. obtaining a sleeve 500 having the characteristics and functions described above, see FIG. 11;

C. obtaining a modified charging handle 400 having the characteristics and functions described above, see FIG. 11;

D. disassembling the firearm 1, at least to the extent of removing the closed gas tube and the gas piston 300;

E. placing the sleeve 500 over the shaft 310 of the gas piston 300;

F. reassembling the firearm 1, whereby the modified gas tube 200 is substituted for the closed gas tube 34 and the gas piston 300 with the sleeve 500 placed over its shaft 310 is inserted into the modified gas tube 200; and

G. attaching the modified charging handle 400 to the sleeve 500.

Steps A-D of the method may be performed in any order, step E may be performed any time after steps B and D and before step F, step F may be performed any time after steps A, B, D, and E, and step G may be performed any time after steps B and C.

In an alternative method, the optional step H may be performed at any time relative to steps A-G, with step H involving removing the right side charging handle 32 from the firearm 1.

Referring now to FIGS. 13-18, additional embodiments of the present invention are disclosed. Unlike the previously disclosed embodiments, in each of the embodiments therein disclosed, the modified charging handle 1400 does NOT reciprocate along with the gas operation of the weapon, an often desirable feature. In this regard, the operator is not exposed to external moving parts, such as the charging handle 400 which does reciprocate with the firing of the host weapon at whatever rate of fire being employed.

Modified gas tube 1200 is provided having a lateral aperture 1220 running along its left side. Lateral aperture 1220 is configured to allow charging handle 1400, which is affixed to charging tube 1500, to extend through the left side of the modified gas tube 1220 when it is in the forward position. A detent may be provided near the front of lateral aperture 1220 for retaining charging handle 1400 in a passive position when not being manually actuated. A cocking notch 1230 may be provided near the upper rear of the lateral aperture for locking charging handle 1400 in a bolt open condition. A sight rail 1600 may be provided atop modified gas tube 1200 and configured in any number of common arrangements, such as the MIL-STD-1913 rail, STANAG 2324 rail, or simply referred to as a “Tactical Rail” standardized mounting platform, as generally depicted in FIG. 14. The sight rail 1600 may be affixed to modified gas tube 1200 in any number of ways, including without limitation, screws, welds, adhesive, tongue and grove, or otherwise machined as a unitary portion of the modified gas tube itself. Components of the gas piston sleeve assembly 1304 may be fabricated from any durable material suited for the application, including without limitation, hardened steel, type 4140, stainless steel, and finished in one of several ways including, without limitation, nitrite and chromium.

Bifurcated sleeve members 1300 a and 1300 b are provided and are configured having an inside diameter, when assembled and held in place with locking bushing 1302, to fit snugly about the shaft 310 of gas tube 300. When locking bushing 1302 is coupled to bifurcated sleeve members 1300 a and 1300 b, it forms an integrated gas tube sleeve assembly 1304. Once assembled on the shaft 310 of gas tube 300, it may be secured into its rearmost position using any number of common fastening means (not shown), such as a drive pin or set screw, or may be welded or fixed into place with adhesive. The forward edge of locking bushing 1302 is configured to have substantially the same diameter as charging tube 1500. Thus when the charging handle 1400 is drawn toward the rear of the weapon 1, the charging tube 1500 to which it is connected, travels rearward as well and its rearmost face abuts against the foremost face of the locking bushing 1302 portion of the gas piston sleeve assembly 1304, thus urging the bolt carrier 46 and each of its corresponding components toward the rear of the weapon. In this manner the weapon 1 becomes manually charged. If it is desired to keep the bolt open after charging, charging handle 1400 is directed into cocking notch 1230 where it will retain the bolt in an open condition until released.

Looking now to FIG. 16, an alternate embodiment of the present invention is therein disclosed. This embodiment is similar to that shown in FIG. 15, except that in this arrangement the gas piston sleeve assembly 1304 is replaced by a cylindrical block 1322 which may be machined as part of a modified gas piston 1320. Like the arrangement shown in FIG. 15, this configuration uses the rear face of charging handle 1500 to engage the leading face of the cylindrical block 1322 to urge bolt carrier 46 rearward when the charging handle 1400 is drawn rearwardly. While this embodiment may be less desirable to some because more components of the host weapon 1 are affected, namely the gas piston 300 which is replaced with modified gas piston 1322, the arrangement has the advantage of fewer component parts (3 versus 5) than previously discussed. The fewer the number of components the easier installation and the fewer components that can fail. As with each of the embodiments of the present invention, this one contemplates being utilized to retrofit into existing firearms 1 in order to provide the operator with a faster, less cumbersome and more accurate charging system.

What has been described and illustrated herein is a preferred embodiment of the invention along with some it its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention as defined in the following claims in which all terms are meant in their broadest, reasonable sense unless otherwise indicated. 

1. A charging mechanism for a firearm, comprising: a generally hollow gas tube including: a sidewall having a first and a second, opposing distal end, and an elongate lateral aperture extending through the sidewall, into the hollow portion of the gas tube; a generally hollow charging tube having a charging handle extending generally laterally therefrom, the charging tube being slidably disposed within the hollow portion of the gas tube, the charging handle extending through the lateral aperture of the gas tube; an elongate, slidable gas piston assembly slidably disposed within the hollow portion of the charging tube; a bifurcated sleeve having a first portion and a second portion, the first and second portions being attached to the gas piston assembly in opposition to one another; and a locking bushing slidably engaging the first and second portions of the bifurcated sleeve, the locking bushing securing the first and second portions to the gas piston assembly, the charging tube being slidable along the hollow portion of the gas tube to selectably engage the locking bushing, thereby urging the gas piston assembly away from the first distal end of the gas tube, the charging tube being reciprocably slidable within the gas tube.
 2. The charging mechanism of claim 1 wherein the gas tube further includes: a cocking notch extending through the sidewall and into the hollow portion of the gas tube, the cocking notch being in communication with the lateral aperture, and the charging handle being selectably retained by the cocking notch.
 3. The charging mechanism of claim 1, further comprising a sight rail section coupled to the gas tube.
 4. The charging mechanism of claim 1 wherein the gas tube further includes a rear collar, the lateral aperture further extending through the collar, into the hollow portion of the gas tube.
 5. A charging mechanism for a firearm, comprising: a generally hollow gas tube including: a sidewall having a first and a second, opposing distal end, and an elongate lateral aperture extending through the sidewall, into the hollow portion of the gas tube; a generally hollow charging tube having a charging handle extending generally laterally therefrom, the charging tube being slidably disposed within the hollow portion of the gas tube, the charging handle extending through the lateral aperture of the gas tube; and an elongate, slidable gas piston assembly slidably disposed within the hollow portion of the charging tube, the gas piston assembly including an integral cylinder block, the charging tube being slidable along the hollow portion of the gas tube to selectably engage the cylinder block, thereby urging the gas piston assembly away from the first distal end of the gas tube, the charging tube being reciprocably slidable within the gas tube.
 6. The charging mechanism of claim 1 wherein the gas tube further includes: a cocking notch extending through the sidewall and into the hollow portion of the gas tube, the cocking notch being in communication with the lateral aperture, and the charging handle being selectably retained by the cocking notch.
 7. The charging mechanism of claim 5, further comprising a sight rail section coupled to the gas tube.
 8. The charging mechanism of claim 5 wherein the gas tube further includes a rear collar, the lateral aperture further extending through the collar, into the hollow portion of the gas tube. 